1. Field of the Invention
The present invention relates to a high concentration surfactant slurry containing a large amount of an internal olefin sulfonate. More specifically, it relates to a high concentration surfactant slurry containing 55% to 75% by weight of olefin sulfonates containing at least 50% by weight of internal olefin sulfonates and having a low viscosity.
2. Description of the Prior Art
Internal olefin sulfonates are surfactants having excellent wetting power and low-temperature stability (or solubility) and suitable for use as detergents and surfactants for enhanced oil recovery (EOR) methods. Internal olefin sulfonates are advantageously used in the form of a high concentration slurry, as in alkylbenzene sulfonates and other surfactants, from the standpoint of efficiency of the storage vessels or containers and the economics of transportation. However, a high concentration slurry containing 50% by weight or more of surfactant generally has a problem in that the viscosity of the slurry is undesirably increased to cause troubles in handling. Various techniques have been developed to produce low viscosity, high concentration slurries containing alkylbenzene sulfonates, alpha-olefin sulfonates (AOS), and polyoxyethylene alkylether sulfates. For example, the addition of inorganic halogen salts such as sodium chloride (U.S. Pat. No. 3,954,679), the addition of polyethyleneglycol (Japanese Unexamined Patent Application No. 50-116383), and the addition of an excess amount of alkali and alkylene oxide (Japanese Examined Patent Application No. 55-16504) have been proposed.
However, the viscosity of a high concentration slurry of internal olefin sulfonates cannot be effectively reduced by the use of the above-mentioned viscosity reducing techniques although these can reduce the viscosity of a high concentration slurry of alpha-olefin sulfonates having structures similar to those of the internal olefin sulfonates. This is because the viscosity behavior of the slurry containing a high concentration of internal olefin sulfonates differs considerably from that of slurries containing a high concentration of alpha-olefin sulfonates andd alkylbenzene sulfonates.